No announcement yet.

Rack and Pinions

  • Filter
  • Time
  • Show
Clear All
new posts

  • Rack and Pinions

    What's a good way to assemble rack and pinion gears? I have an assembly that I am trying to design, but I can't seem to crack the code on getting the gears to mesh correctly. It seems that whatever I do, either the pinion gear is too small or too big. I tried the gray gears and the double bevel. I want to use the small snap on rack gears so I can make the rack whatever length I want.
    Norfolk, Virginia, USA
    FLL Coach and Regional Tournament Head judge since 2014

  • #2
    What I have found when doing this type of rack gearing is to use regular lego plates (1x4, 1x6, 1x8, etc) to "build up" the rack to fit the various gear combinations. This also has the benefit of interlocking the rack assembly so that the overall assembly is stronger when it is extended beyond any support you may have.
    2014 World Class Learning (coach Stealth Bots #3233)
    2015 Trash Trek (coach Electric Trashbeards #8039)
    2016 Animal Allies (coach Plank Robit Rovers #8039)
    2017 Hydrodynamics (coach Rogue Robotics #30453)
    2018 Into Orbit (coach Rogue Robotics #30453)
    2019 City Shaper (coach Rogue Robotics #30453)


    • #3
      I noticed you are using an open beam to support the axle and pinion gear. You may want to consider some other blocks to perform this function. You could use cross-blocks in various combinations which may give you more flexibility in determining the height of the pinion gear to the rack. See: as examples of using smaller cross blocks.


      • #4
        That rack is "1/2 tall", so you need to somehow make that difference.
        Legolympians - 2009-2015 (retired - joined FRC team 5422 Stormgears)
        Legolicious - 5th year girls team
        Brick Force - 2nd year boys team

        2015 - Mass FLL coach of the year.


        • #5


          The key is to understand several things:

          - Which gears mesh with which, when spaced across a beam.
          - How the height of bricks correlates with hole spacing.
          - How to support the gears so they don't slip or bind.
          - [SPOILER ALERT] Don't be afraid to use classic pieces (flats, 1st gen Technic hole bricks)

          That grey frame really limits your flexibility. Build in layers to match the spacing correctly.

          Everyone's shooting for Strength Exercise.
          But, seriously, we use the forklift for almost all of the missions. If you can get it to work, it's an awesome tool. Aside from the lifting strength, you can set it up for multiple missions on the same run.


          • #6
            mageus already hit the high points in Post #5. The important details are that racks are 0.6 modules thick, and plates are 0.4 modules thick. So, thudthud was quick with the "right" answer: putting plates between the racks and the half pins in your model will cause the racks to mesh a Z8 (tiny) gear perfectly.


            • #7
              Yep. The kids figured it out! Plates under the racks were the key.
              Norfolk, Virginia, USA
              FLL Coach and Regional Tournament Head judge since 2014